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My BP-60 success story!

Well, after a few (ahem) years of working on my pet BP-60 project, I met with success today- 45 minute bottom time (in cave) at 90 feet- 2.6 cf of diluent consumed! Yea!

I've been working on this project for some time as a gas extender for my sidemount rig- It has had a few dives prior to this, but all O2 only, as the Munro board had not been installed. Got that finished last month.

There are a lot of proof-of-concept items on the rig, not the least of which are Legris push to connect fittings and plastic 250PSI tubing used throughout. (Which, I am happy to report, doesn't leak at all, and is SUPER easy to work with.)

The basic BP60 counterlung case, diapharagm, scrubber, cover, and ADV are really the only parts I have kept, everything else was binned. The counterlung and steel cover will soon be replaced with a deeper version, in hopes of increasing the run time and reducing the possibility of early breakthrough. (Haven't seen it yet.)

The counterlung case is mounted on a homemade stainless steel frame which provides bulkheads for mounting all the hose connections. This is also connected to a lower steel frame that provides the connection for the harness straps (really only straps that attach to my sidemount harness) and retains the counterlung return spring.) These two parts add just enough weight to make the rig neutral with the counterlung partially filled, and completely eliminate the plastic housing that added breathing resistance.

Both Oxygen and Diluent are offboard, using Swakelok DESO quick connects. Oxygen addition is via a miniature plastic orifice, which just happens to have barb fittings that fit into the plastic tubing used in all the Legris fittings. Inline barbed filter on either side. (Had an earlier orifice get clogged between dives before I added the filters- the jury is still out on the filters.) The orifice and filters are so cheap I have a box of them in case it turns into a problem.

Manual Oxygen and Diluent addition are also included via a dual inflator handset, Oxygen on one side, Diluent on the other. This works fantastically, though in the future, the buttons will become different shapes, as in a pinch, it might be easy to add the wrong gas, as they feel the same even though they are on opposite sides of the handset.

I now have one of Jacob's BOV (golem gear) which I am sorry to say actually breathes better in OC mode than most of my regulators. :D I have to agree with all that this is a fantastic piece of kit, and even the slightest hint of overbreathing the scrubber and I am off on OC, with a quick twist.

The sensors are a bank of K1Ds (only thing I could fit) run to a Munro V1 board, which works very well, but is a little ungainly and large, and I will eventually build a much smaller one, perhaps with one of his new boards! :)

And for the dive report- Mounted the BP60 on the back of my sidemount rig (SM120s). This still leaves my chest area clear, which I like, as this is the deployment area for my OC regulators (attached to a neck loop.) The loop hoses are a little short, which means there is just enough room for the BOV to sit away from my mouth while standing, and is a little snug around the neck, but when in the water, it seems to work fine, and I can turn my head, without the hoses floating, despite having no hose weights. The LP hose feeding the BOV is a little long, so that flaps somewhat.
The addition handset sits over my right shoulder d-ring (mirrors my wing inflator on the other side) and is very easy to reach, and actually, you can see it with the loop in your mouth.
Once in the water, with the O2 bottle turned on and plugged in, the O2 level slowly climbs, as it should, so I prebreathed the rig for a couple of minutes to bring the loop O2 down, introduce fresh diluent and heat up the scrubber.

Once that is all under control, my safety diver and I decend into the cavern (which is crystal clear blue today) and we start a slow swim into the cave, with me eyeballing the display every second or so. (OK, I'm actually holding it in one hand, my light in the other.) As we decend in depth the ADV adds gas before it gets difficult to breath, and the PO2 increases as it should. Once at depth (90 feet) the O2 remains very stable, which means I have the O2 set right, at 0.5 LPM. We swim at varying rates so I can get a feel for how the machine will work, how easy it is to overbreath, etc.

A comparison- Two weeks ago I dove a friend's KISS Classic. Though I really like that machine (I will eventually have to buy one) the BP-60 breathes a little better than the Kiss, and the ADV is certainly easier to operate, though I understand that is intentional on the part of the Kiss. I felt like I had to suck my lungs out to activate the ADV on the kiss- the BP60 added just as I needed it. I dislike the diluent manual add on the Kiss- though in truth, I'm not really sure when you would have to manually add diluent when you could just exhale from the mask, but having the diluent add easily accessible was nice. (Never had to use it, so hmmm.) O2 manual addition is very similar in feel, though I like having it on a short and controlled hose, rather than flying around like the Kiss one. Only used that to boost O2 for deco. Overall, the BP60 is lighter, and a bit tail heavy, due to my use of a rear-mounted AL14 for O2, the Kiss was perfectly balanced when bolted to the back of my sidemount rig. I liked the pendant display on the Kiss, will soon have one similar on the BP60.

Some notes.

The scrubber can definately be overbreathed. I intentionally tried to overwork it, swimming really fast against the flow, and after about 20 seconds switched to OC for a couple of breaths and purged the loop. This took care of the problem, but for an extended heavy swim, I might be in trouble. However, even If I had to switch back and forth, I would save more gas than if I was just OC.

The feed hose for the BOV is too long- it swings wide of the rest of the hoses.

Another 2 inches of loop hose length wouldn't hurt.

Anyway, hope someone got something out of this- no pictures of yet, I dont know anyone here with a camera and spare time, but I will try to add a couple of captures of the CAD drawings which show the frame parts and the handset.

Dive number two!

Unit is still working great- stretched the scrubber out to 130 minutes today on another dive at Jackson Blue. This is about the fourth dive using the larger dragersorb that I had left over from another project. It will be interesting to see if i get better run time from the scrubber with a finer sorb.

4 hour dive on BP60 in cave! YEA! ..

Solid 4 hour dive in cave on the BP60 today. did not have any CO2 issues, which makes me happy. I adjusted the O2 feed from 0.6 to 0.8 LPM which turns out is much closer to the right number for me. I did not have to manually add any O2 or diluent throughout the entire dive. One thing I did notice that was annoying: I develop a significant amount of lung phlegm at the exhaust side of the BOV. It does not travel further into the loop by itself, so after about 80 minutes it is sort of like exhaling into a shallow bit of water. The remedy seems to be go to an OC reg and hold the BOV over my head and shake the water down into the diapharagm area by jiggling the outlet hose. This seems to work for about an hour or so each time. Exhaling into the phlegm is not really a problem, just sort of annoying, and loud, compared to everything else. And some stats- 8.6CF of oxygen used through the orifice and then upped for 100% deco. 11CF diluent used, loop only, suit and wing are off bailout gas.

Ok, dave here are some photos-
Here are the banjo fittings that replace the original fittings. I got an original idea from someone on this board, but theirs were not easy to remove- mine have a fixed outer housing to which the pipe is soldered, and the inner bolt rotates for easy removal. (This is also how I test my O2 flow- the aft fitting comes out and screws into my flow meter.
This is the diapharagm retainer. It replaces the huge plastic case, as I wanted this rig as small as possible. It also adds some weight, being stainless steel. The rig can be removed in the water and pushed in front of me (you have to be open circuit, the BOV doesn't rotate) and with the two stainless brackets it is neutral in the water with the counterlung half full.
This is the O2 and DIL addition block. I dont like how the Kiss addition block flops around on its six foot cords, so mine is short and sits just below the right shoulder d-ring. So far, I have not had to use it at all during the dive, and I am debating the use of the diluent side at all- but perhaps I will find a reason to use it some day. Design note- the two sides are easy to confuse as the buttons are the same shape- it would be very easy to hit the wrong button. Fortunately, hitting either button will increase the O2, so it doesnt really matter. I dont train to decrease o2 by manual add- I exhale through the mask- the machine fixes itself with diluent addition. (I do plan to make the O2 button a different shape though.
Here is the whole rig ready to mount over my sidemount rig and go in the water.
Here is the magic- Notice that all of the plumbing is soft tubing- 250psi max with legris fittings. This stuff absolutely rocks. You just cant accidentally dislodge a fitting- I've tried, and they dont leak. I suppose they might eventually, but then I just swap out any of the fittings- 5 second job. Same with tubing. The orifices are so cheap they come in packs of 10- same with the filters. If they screw up (only did it once, before I added filters) I just swap the whole assembly. I can get back with the name of the orifice- I dont have the box with me.

Re: My BP-60 success story!

It's getting a lot of use now- here is a pic of me diving in Yucatan, Mexico.
This is the 3rd hour of the dive, 160 feet of water, just before starting deco, laying a line to some archaeological artifacts in the cave. Third dive in three days, similar profile. The rig works sweet. I just have to deal with the flying display (Shearwater here I come) and it will be complete.

Re: My BP-60 success story!

Jason,

What's the dry travel weight for the rebreather with the stainless steel ring included?

With the K1d sensors can you use a Shearwater- or does it require R22’s for sensors. I have found that most computers want the R22 style another reason Jetsam went over to the R22 sensors on the sport units.

In respect to the single counterlung which way did you run it compared to the scrubber (counterlung before or after?) I believe the standard is through the scrubber and then into the counterlung (or after the scrubber.)

With your current dives, how much do you estimate you are using of the scrubber as a percentage?I was curious if you were analysis what you are using of the bed.

Re: My BP-60 success story!

Originally Posted by Crazyduck

Jason,

What's the dry travel weight for the rebreather with the stainless steel ring included?

Bathroom scale says 19.0 lbs, empty scrubber. This does not include onboard O2 tanks (which is not shown in the pic anyway). Actually, with the scubber full, and the counterlung half full, it is neutrally bouyant- I can deflate it and it sinks, or inflate and it floats above the surface. Perfect for donning and doffing in cave. The ring does not come off- it is integral to the function of the unit. (I would have to completely strip the center section to take it off, and it retains the counterlung spring.)

Originally Posted by Crazyduck

With the K1d sensors can you use a Shearwater- or does it require R22’s for sensors. I have found that most computers want the R22 style another reason Jetsam went over to the R22 sensors on the sport units.

I do not know the answer to this, but it matters little- there is room for a triple R22 sensor block in the same place that the K1Ds are mounted- as soon as they die, I will make the block and replace them with R22s anyway.

Originally Posted by Crazyduck

In respect to the single counterlung which way did you run it compared to the scrubber (counterlung before or after?) I believe the standard is through the scrubber and then into the counterlung (or after the scrubber.)

Counterlung is before- this is more for the mechanics of the center section than for any other reason- The counterlung is mounted below in almost all conditions- in addition, there are ledges that prevent water from flowing upward towards the scrubber inlets if you go vertical- almost as if it was designed to run that way in the water. In addition, any possible water dumping will happen in the counterlung- though due to the shape of the OP valve, this is not really possible either- but if the unit is run the other direction, water (lung scum) from the the loop is sent directly onto the scrubber and soaks it right away. Not acceptable. Excess water in the counterlung is still a slight problem- so far it is never gotten into the scrubber, but I can definately hear it sloshing around after 4+ hours. I suppose that I should leave well enough alone in the fact that water has not yet made it to the scrubber, but on the other hand I have been tossing around the possibility of adding a water dump at the base of the counterlung. I just hate to make another penetration into the cannister.

Originally Posted by Crazyduck

With your current dives, how much do you estimate you are using of the scrubber as a percentage?

I would say almost 95%. I have had a number of dives where i have split the scrubber into two dives with anywhere between hours and a day in between- and always about hour 4 I seem to start getting CO2 effects, such as increased rate of breathing, but never headaches that approach what I can get OC. This may very well be attributed to using scrubber that expired in 1992. Since all that is gone now, I will revise my numbers when I get some new sofnolime next month. I have not experienced effects on a single dive, even as long as 4.5 hours. So all that is not very scientific, or even very smart, but hey.

Originally Posted by Crazyduck

I was curious if you were analysis what you are using of the bed.

Nothing beyond diving it and seeing what happens.

Originally Posted by Crazyduck

Great system and very interesting use of the push piping.

Thanks, I cant begin to impress on folks how awesome this tubing is. It just never leaks. I have regular scuba stuff that leaks more often than this tubing. Great stuff.

Re: My BP-60 success story!

Originally Posted by Crazyduck

Jason,

With the K1d sensors can you use a Shearwater- or does it require R22’s for sensors. I have found that most computers want the R22 style another reason Jetsam went over to the R22 sensors on the sport units.

Andrew

I've used the Shearwater GF and now Pursuit with the K1D sensors on my KISS Sport with no problems at all.

Re: My BP-60 success story!

...there is room for a triple R22 sensor block in the same place that the K1Ds are mounted- as soon as they die, I will make the block and replace them with R22s anyway.

Jason

Jason,

Nicely done!

Where do you mount the sensors?

How does the counterlung spring affect the breathing? In its original terrestrial application the BP-60 uses the spring to maintain positive pressure in the loop. Just wondering how this works out in different orientations underwater.